Lighting trends in residential and commercial applications are taking advantage of the increased dimming and color control offered by LED light fixtures. However, the efficiency of a fixture is affected by the color and intensity level of the light output. Energy codes are starting to incorporate color tunable products and expectations for efficiency across the tunable range. Thus, there is a need for a lighting product which is efficient across a wide range of intensities and color temperatures.
There is a demand for light sources that produce adjustable white light across a range of correlated color temperatures (CCT or color temperature), such as from about 6000K to about 1800K; products of this type are often called tunable white products. There is also a demand for light sources that provide light with a warm color temperature, such as from about 2700K to about 1800K, especially if the light intensity may be dimmed; products of this type are often called warm dimming products. Additionally, there is a demand for high-efficiency lighting products, to improve energy budgets and to meet energy efficiency standards. However, when using LED light fixtures, warmer color temperatures are historically of lower efficiency, as LEDs of warmer colors require a less efficient phosphor coating to counteract the blue color of the underlying diode, necessitating more and brighter LEDs to reach a given level of illumination. In existing products, a product is typically either a warm dimming product or a tunable white product. It is desirable to have a product with benefits of both without suffering decreased energy efficiency at lower CCTs.
BRIEF SUMMARY
The described system and control method allows a light fixture to have a wider range of color temperatures while limiting the warmest temperature reached at full intensity. The CCT and the intensity of the light output may be controlled independently across a certain range, and may be dependent across another range. In an implementation of the system, the light output may have allowed combinations of CCT and intensity.
In an implementation of the system, a light fixture may be configured to provide a range of CCT (e.g., from about 1800K to about 6000K), and a range of light output intensity (e.g., from about 0% output to about 100% output). In a further implementation, the particular levels of the CCT and the intensity may be controlled by a driver, such as an LED driver, and a programmed controller, such as a microprocessor, may control the driver and receive values from a user interface. In another implementation, one or more user interfaces, or handles, may provide control inputs having a value. A value associated with a control input may be received by the programmed controller, such that the controller may control the driver, and the driver may adjust the light output based on the received value. In one implementation, sometimes referred to as single-handle control, both intensity and CCT of one or more light fixtures may be adjusted based on received values from a single handle. In an alternative implementation, sometimes referred to as dual-handle control, intensity of the one or more light fixtures may be adjusted based on received values from a first handle, while CCT may be adjusted based on received values from a second handle. Further implementations may comprise additional handles to provide adjustments for additional parameters such as delta-uv (i.e., tint), color (e.g., red-green-blue blends), color rendering index (CRI), circadian stimulus, TM-30 metrics, spatial arrangements, or other qualities of the light output.
In an implementation featuring single-handle control, a single handle may provide a value to a controller, wherein the value is related to a relative position of the single handle based on an available range of possible positions. In a further implementation, the available range of positions may be divided into two or more zones; zones may be overlapping or non-overlapping. In another implementation, the controller may determine a requested value from the value received from the single handle, and the controller may further determine that the requested value corresponds to light output within a range of intensity levels (e.g., from about 0% intensity to about 100% intensity) and within a range of CCT levels (e.g., from about 1800K to about 6000K). In yet a further implementation, the controller may determine a correspondence between the requested value and the CCT level when the received value is within a first zone, and a correspondence between the requested value and the intensity and CCT levels when the received value is outside of the first zone.
In an implementation featuring dual-handle control, a controller may receive values from a first handle and a second handle, wherein each received value is related to a relative position of each handle. In a further implementation, the value received from the first handle may be associated with a requested intensity, and the value received from the second handle may be associated with a requested color temperature. In a further implementation, the controller may receive a value from the one or more handles and determine a requested value from the received value. In a further implementation, the controller may determine that the requested value corresponds to an allowed combination of color temperature and intensity, or the controller may adjust the requested value to obtain an allowed combination of color temperature and/or intensity. In another implementation, the controller may control the LED driver such that the light fixture produces color temperature output and intensity output corresponding to either the allowed combination or the obtained combination. In a non-limiting example of this implementation, the CCT of the light output may be limited to cooler levels when the intensity is higher, and/or the intensity of the light may be limited to lower levels when the CCT is warmer.
For both single- and dual-handle implementations, the available range of positions of a handle may be divided with an additional zone, and input from the handle may adjust a different light parameter of the light output, such as delta-uv (i.e., tint), color (e.g., red-green-blue blends), color rendering index (CRI), circadian stimulus, TM-30 metrics, spatial arrangements, or other parameters, when the handle position is within the additional zone. The adjustment of any parameter of the light output may have a linear relation to the position of the handle, a non-linear relation, a step-wise relation, or any other suitable relation. The relative relation of the handle position and the light parameter may change during operation, for example in a dual-handle implementation, or for a first zone compared to a second zone.
The values, ranges, and thresholds provided herein are exemplary only, and may be changed without departing from the scope and spirit of the invention. Similarly, relative positions of the handle controls are exemplary, and different relative positions may be used without departing from the described invention.